neformatnoe,
http://learn.javascript.ru/form-elements#select-option
<!DOCTYPE HTML>
<html>
<head> </head>
<body>
<select id="country">
<option value="cou1">country1</option>
<option value="cou2">country2</option>
<option value="cou3">country3</option>
</select>
<br>
<input type="text" id="inpCountry" placeholder="inpCountry"><br>
<script>
var country = document.getElementById('country'),
inpCity = document.getElementById('inpCity');
country.addEventListener('change', countryChange, false);
function countryChange () {
var option = country.options[country.selectedIndex||0]
inpCountry.value = option.value + " " + option.text;
}
</script>
</body>
</html>